Educational Use Only - Embryology is an educational resource for learning concepts in embryological development, no clinical information is provided and content should not be used for any other purpose.

Introduction

No smoking sign

There is an association between physical defects among newborns and maternal smoking tobacco during pregnancy.

Spontaneous abortion, ectopic implantation, pre-term births, low-weight full-term babies, and fetal and infant deaths all occur more frequently among mothers who smoke during pregnancy than among those who do not. These developmental abnormalities are therefore environmental (maternal) in origin and not congenital (though there are probably genetics involved with a tendency to smoke).

The possible relationship to preterm birth generates one major clinical problem, as preterm birth results in 47% of all neonatal deaths (UK data).

Also of great concern is that smoking is a suggested causative factor for low infant birth weight (LBW) (2.500kg and below). LBW is in turn related to future (postnatal) health by the fetal origins hypothesis.

Some Recent Findings

The effects of electronic cigarette emissions on systemic cotinine levels, weight and postnatal lung growth in neonatal mice[1] "Electronic cigarette (E-cigarettes) emissions present a potentially new hazard to neonates through inhalation, dermal and oral contact. Exposure to nicotine containing E-cigarettes may cause significant systemic absorption in neonates due to the potential for multi-route exposure. Systemic absorption of nicotine and constituents of E-cigarette emissions may adversely impact weight and lung development in the neonate. ...These studies indicate that exposure to E-cigarette emissions during the neonatal period can adversely impact weight gain. In addition exposure to nicotine containing E-cigarettes can cause detectable levels of systemic cotinine, diminished alveolar cell proliferation and a modest impairment in postnatal lung growth." Respiratory System Development

Helping pregnant smokers to quit[2] "Although most smokers manage to quit during pregnancy, a proportion does not. In England, 26% of women smoke in the year before their pregnancy and 12% smoke through to delivery.1 The rate is similar in other high income countries, whereas in low and middle income countries, smoking rates are more variable and seem to be increasing among young women.2 In addition to the countless negative consequences for the smoker’s own mental and physical health, smoking in pregnancy is linked to a wide range of poor health outcomes for the child.3 Thus there is an urgent need to help pregnant smokers who find it difficult to quit."

Smoking overrules many other risk factors for small for gestational age birth in less educated mothers.[3] "In this study fully completed data were available for 3793 pregnant women of Dutch origin from a population-based cohort (ABCD study). Path-analysis was conducted to examine the role of explanatory factors in the relation of maternal education to SGA. ...Among a large array of potential factors, the elevated risk of SGA birth among low-educated women appeared largely attributable to maternal smoking and to a lesser extent to maternal height. To reduce educational inequalities more effort is required to include low-educated women especially in prenatal intervention programs such as smoking cessation programs instead of effort into reducing other SGA-risk factors, though these factors might still be relevant at the individual level."

Influence of Smoking and Alcohol during Pregnancy on Outcome of VLBW Infants[4] "Nicotine and alcohol consumption have been associated with premature delivery and adverse neonatal outcome. We wanted to analyze the influence of self-reported nicotine and alcohol consumption on outcome of VLBW infants.In an ongoing multicenter study 2 475 parents of former very low birth weight (VLBW) infants born between January 2009 and December 2011 answered questionnaires about maternal smoking habits and alcohol consumption during pregnancy. ...Smoking during pregnancy results in a high rate of growth restricted VLBW infants. Prenatal exposition to nicotine seems to increase postnatal complications such as BPD und ROP."

Maternal smoking during pregnancy and kidney volume in the offspring: the Generation R Study[5] "An adverse fetal environment leads to smaller kidneys, with fewer nephrons, which might predispose an individual to the development of kidney disease and hypertension in adult life. ... Among mothers who continued smoking, we observed dose-dependent associations between the number of cigarettes smoked during pregnancy and kidney volume in fetal life. Smoking less than five cigarettes per day was associated with larger fetal combined kidney volume, while smoking more than ten cigarettes per day tended to be associated with smaller fetal combined kidney volume (p for trend: 0.002). This pattern was not significant for kidney volume at the age of 2 years. Our results suggest that smoking during pregnancy might affect kidney development in fetal life with a dose-dependent relationship."

Quantitative effects of tobacco smoking exposure on the maternal-fetal circulation[6] "In pregnant women who smoke, higher arterial resistance indices and lower birth weights were observed, and these findings were associated with increasing levels of tobacco smoking exposure. The values were significantly different when compared to those found in non-smoking pregnant women. This study contributes to the findings that smoking damage during pregnancy is dose-dependent, as demonstrated by the objective methods for measuring tobacco smoking exposure."

More recent papers

This table shows an automated computer PubMed search using the listed sub-heading term.

Therefore the list of references do not reflect any editorial selection of material based on content or relevance.

References appear in this list based upon the date of the actual page viewing.

References listed on the rest of the content page and the associated discussion page (listed under the publication year sub-headings) do include some editorial selection based upon both relevance and availability.

Nicotine

Nicotine is a natural ingredient in tobacco leaves, where as an alkaloid it provides some protection for the plant being eaten by insects by acting as a botanical insecticide.

Tobacco also contains other minor alkaloids nornicotine, anatabine and anabasine.

There is a chemical datasheet for nicotine, the pure chemical, note that commercial tobacco products include many additional chemicals.

Neonates have a decreased ability to metabolise nicotine, with a 3-4 times longer half-life in newborns exposed to tobacco smoke compared with adults.

Cytochrome P450, Subfamily IIA, Polypeptide 6 (CYP2A6) is the main enzyme in the liver responsible for metabolism (oxidation) of nicotine. (More? OMIM Entry CYP2A6) and there are known mutations that occur in this gene which would also impact on nicotine metabolism.

Carbon Monoxide

Mouse carbon monoxide exposure

Smoking tobacco is also a source of carbon monoxide (CO), a colourless and odorless gas formed mainly as a by-product of incomplete combustion of hydrocarbons and can cause cytotoxicity by tissue hypoxia.

A recent study has identified in a newborn mouse model, effects on neurodevelopment of even sub-clinical levels of carbon monoxide.[7]

Carbon monoxide:

enters circulation though the respiratory system

binding to haemoglobin to form carboxy-haemoglobin (COHb)

haemoglobin affinity is 240 times greater than for oxygen

fetal haemoglobin binds with even greater affinity

tissue hypoxia occurs when COHb levels are greater than 70%

Australian National Drug Strategy Household Survey 1995

Below are excerpted statistics from the 1995 household survey.

Smoking is higher among young women than young men, although males tend to smoke more heavily. Among 14-19 year olds: 13% are current regular smokers, 5% are occasional smokers, while 49% have never smoked.

For more information please email CEIDA Information Centre

Passive Smoking

Exposure of non-smokers to environmental tobacco smoke, "passive smoking", has been associated with a substantial increased disease risk (coronary heart disease, cancer) a recent study now adds diabetes to the possible deletirious effects. Houston TK, Kiefe CI, Person SD, Pletcher MJ, Liu K, Iribarren C. Active and passive smoking and development of glucose intolerance among young adults in a prospective cohort: CARDIA study. BMJ. 2006 May 6;332(7549):1064-9. "These findings support a role of both active and passive smoking in the development of glucose intolerance in young adulthood."

Smoking and Pregnancy

Smoking doubles the risk of having a low-birthweight baby and significantly increases the rate of perinatal mortality and several other adverse pregnancy outcomes.
The mean reduction in birthweight for babies of smoking mothers is 200 g.
High quality interventions to help pregnant women quit smoking produce an absolute difference of 8.1% in validated late-pregnancy quit rates.
If abstinence is not achievable, it is likely that a 50% reduction in smoking would be the minimum necessary to benefit the health of mother and baby.
Healthcare providers perform poorly in antenatal interventions to stop women smoking. Midwives deliver interventions at a higher rate than doctors.
The efficacy of nicotine replacement therapy has not been established in pregnancy. Currently, its use should only be considered in women smoking more than 10 cigarettes per day who have made a recent, unsuccessful attempt to quit and who are motivated to quit.
Relapse prevention programs have shown little success in the postpartum period.
Data from: Quitting smoking in pregnancy Raoul A Walsh, John B Lowe, Peter J Hopkins (MJA 2001; 175: 320-323)

Placental Function

A review[8] of three placental markers showed "maternal smoking impairs human placental development by changing the balance between cytotrophoblast (CTB) proliferation and differentiation"

Australia

Data in this graph from AIHW 2014 Report, Birthweight of babies born to Indigenous mothers.[9]

Search Pubmed

External Links

External Links Notice - The dynamic nature of the internet may mean that some of these listed links may no longer function. If the link no longer works search the web with the link text or name. Links to any external commercial sites are provided for information purposes only and should never be considered an endorsement. UNSW Embryology is provided as an educational resource with no clinical information or commercial affiliation.